So my question is this, I know the close ratio 6 speed in the STi is pretty bulletproof and the 5 speed in the WRX has had its issues. Do you think an STi would ever go away with the 6 speed and go to a 5 speed? The new STi's are actually slower 0-60 than the WRX is. Is the 6 speed a hinder to the STi?

No. The 6-speed on the STi is not designed for drag racing. From a stop, from a rolling start, for straight line acceleration on flat tarmac of substantial distances (>1/8 mile or so). It's a rally car, short geared to provide the optimum gear for short bursts of acceleration through varying speeds between 0mph and ~100mph. The STi sold is a mass produced knock off of the rally car made to meet general safety, emissions, and reliability specifications of a street car. The WRX, in turn, is a purposely degraded version of that formula.

The WRX is a little further from it's rally heritage than the STi. As such, it makes sense to give it a much cheaper transmission to keep costs down and have a more attractive pricepoint. Also, since it is not intended for more serious motorsports, it is given a drive ratio that fits better with the target audience. As such, it's a better gearing for drag racing.

Would a guy who bought an STi want to make his car a drag car? Maybe. That person bought the wrong car for drag racing. There are cheaper and faster options in a 1/4 mile for sure. AWD is a burden on the drag strip giving lots of extra weight and drivetrain losses, as is an extra pair of doors and framework. There are guys who like the multi-purpose nature of the STi but may want to drag it on occasion and work at it from that angle.

Would a drag oriented STi driver ever use a 5-speed? Not one from a WRX. The WRX 5-speed is barely enough to handle stock WRX power levels. It's not robust and is not designed for any kind of shock loading at all. There are 5-speed custom built transmissions out there that are quite good on a drag strip but they share very little in common with the one in your car. They have 5 gears, but that's about it. One reason there are so many aftermarket 5-speed gear sets and so few aftermarket 6-speed gear sets is because the WRX 5-speed breaks so much more often than the STi's 6-speed.

So should your buddy be jealous of your transmission because he bought an STi? God I hope not. That'd be like saying he cared who was faster between the two in a 1/4 mile. Meanwhile, the 25 year old rust bucket foxbody sitting in the corner with some used drag radials and a few grand in engine mods is going to make you both look real stupid with a small fraction of your money.

But if the three of you (foxbody tagging along) ever want to race around an ice track, certainly the STi guy will be loving his "extra gear" that's holding back his 1/4 mile time.

Besides. This argument just keeps going in circles which is why bench racing is banned here. The guy in the WRX is basically overpaying for his impreza (which would be much cheaper) with a turbo slapped in. The impreza guy is basically overpaying for a 15 year old version of the same thing. The 15 year old impreza guy is also overpaying compared to a fast honda civic with nitrous that will last a few thousand miles and costs next to nothing while smoking supercars.

There's a car seat in the back seat of my STi. I drive it year round through the snow. I would trade several HP for a few less dings, paint blemishes, and undercarriage rust. I can't remember the last time I used 6th gear. I could care less about my 1/4 mile time. It's not why I bought the car I did.

Mosc,
Really good post! It explained a lot about the difference between the two cars. I have two questions for you,
First, would a 6sp sti transmission be a good upgrade for reliability for a wrx?
Second, because of the ratio change, would the car need a tune?
Also, would this make the car "slower" acceleration wise?
Thanks!

The 5-speed in the WRX is sufficient if you don't drive too aggressively, stick with a stock clutch, and keep power levels somewhat near stock. For those situations where these requirements are not held, it will eventually break. The quality of the driver and the care taken can change that eventuality to within a few hundred miles to never and anywhere in between. Still, the WRX's 5-speed is certainly the main hurdle to surpass when trying to upgrade the car to higher levels of performance.

The 6-speed STi transmission and it's related differentials are extremely robust parts for a street driven 4-door compact car. The STi often sees motorsport use in situations where non-streetable power is not needed with very little modification. Ice racing, rally racing, autocross, all manor of amateur motorsports, it's an extremely well suited car from the factory in no small part due to the strength and flexibility (six short gears) of the drivetrain.

As a possible upgrade for the WRX, it does make some sense. However, the rest of the WRX drivetrain cannot simply be hooked up to the STi 6-speed. Also, the STi 6-speed itself is quite pricy costing as much as $6,000 for a good one, that part alone. Because of the high demand for modification on the WRX and the high rate of WRX 5-speed transmission failures, there are a variety of options available to WRX owners outside of swapping the entire driveline over to the STi's setup. In fact, the STi 6-speed swap into a WRX will likely exceed the cost of selling the WRX and buying the STi with that setup already installed. As such, most people will recommend "If you want the STi's transmission, buy an STi". There are other upgrades between the WRX and the STi (turbo, brakes, DCCD, etc) but the transmission is the most costly.

The aftermarket 5-speed options then are pretty appealing choices to most WRX drivers. They come in a variety of shapes and sizes, the best of which can exceed the STi's 6-speed in strength and shock loading capability. Also, a custom transmission lets the driver choose a gearing that makes sense for their chosen areas of interest (IE, if you want to focus on drag racing). There are also somewhat budget oriented options aiming to get the typical ~300whp WRX back on the road cheaply and reliably.

Do you need to tune your engine for a transmission change? No. Unrelated. Though you may not be considering all the computer related fun of trying to get DCCD to work in a WRX after swapping in the STi's 6-speed. It's a fun process.

Acceleration depends on several variables. You generally want to shift as little as possible between where you start and where you finish. Custom built drag cars typically have only 2 gears. One to get them off the line, the other to make it from there to the finish line. Of course, those cars will be going hundreds of miles an hour by the finish line. You would not want to build a WRX with that kind of thinking. First off, it's a terrible choice for a pure drag car (AWD, 4dr, manual, etc). Second, drag cars aren't much fun for anything other than accelerating in a straight line. If you want to use that round thing in front of you from time to time, you're going to have to consider gearing that makes more sense to start accelerating at other speeds than zero. The STi's 6-speed is considerably better suited than the WRX's 5-speed for several common speed increments. What does that mean? It means the STi's second gear stops at 55mph so it's 0-50 time is better than a WRX. 0-60 requires 2 shifts on the STi, it's not that good a choice for the 6-speed. Also, the STi is going to be faster from cruising RPM's for most of your typical 20-40mph, 40-60mph, 60-80mph, or any such type speed increments. It will have more speeds that sit nicely in the fat part of it's gearing (since it can choose between more gears over those speeds) when acceleration is not just defined as from 0 to as fast as you can go.

All that said, if you wanted a pure 1/4 mile oriented gearing on a WRX, it's going to look pretty tall, taller than anything sold by Subaru. The WRX's 5-speed is considerably taller than the STi's 6-speed. In fact, 6th on the STi is SHORTER than 5th on the WRX (4th on the WRX and 5th on the STi are pretty similar). Rally racing calls for some of the shortest gearing of any motorsport. Drag racing calls for some of the tallest gearing of any motorsport. Hopefully this helps explain that difference.

Stage 2 is more than stock, but not a ton. It increases the risk of transmission failure, but it was not zero when the car was stock. There is no cost effective way to strengthen the WRX's 5-speed. You can minimize the risk on your 5-speed by avoiding shock loading. What does that mean? It means don't rev up the engine before engaging first and make sure the clutch is fully engaged before applying power between gears. Does that sound boring to you? It does to me too but shock loading breaks transmissions.

I would say to you Laszlo that the risk to your transmission is substantial at stock power levels and is only slightly raised at "stage 2" power levels.

The one bit of wisdom that you can use to protect your 5-speed is to use a stock clutch if the one in there wears out. Stock WRX clutches can't handle a ton of torque without slipping and when driven aggressively will wear quicker than you may like but they're also not going to increase shock loading. Slipping a clutch burns clutch, burns money, but it saves transmissions. In comparison, the STi's 6-speed can handle much stiffer than stock clutches. MUCH.